.beta.-(1-6)-endoglucanases (E.C. 3.2.1.75) are enzymes which catalyses the cleavage of .beta.-(1-6) linkages in .beta.-glucan, a major component of the cell walls of fungal (including yeast) cells. These enzymes are also referred to as pustulanases due to their capability of degrading pustulan.
Cell walls of fungal microorganisms such as yeasts and fungi are complex structures which, in addition to .beta.-glucan, comprise a number of other components. For instance, yeast cell walls comprises a protein-mannan complex layer in addition to a glucan layer (Andrews and Asenjo, 1987), and cell walls of filamentous fungi additionally comprise varying amounts of chitin and chitosan (cf. Hudson, H. J., 1986).
It is well-known that microorganisms produce a number of valuable products such as colorants, flavorants, vitamins, the isolation of which is desirable. The isolation of intracellularly produced products requires that the cell walls of the microbial producers be ruptured or lysed.
Because of the complex composition of microbial cell walls, the rupture or lysis of cell walls has traditionally been carried out by rather vigorous treatments involving the use of strong chemicals and/or mechanical means.
Enzymatic lysis and disruption of microbial cells have been suggested as a desirable alternative to chemical or mechanical rupture in the production of yeast extracts or other intracellularly produced products (Andrew and Asenjo (1987), Phaff (1977)). Furthermore, enzymatic lysis has been suggested for use in the preparation of protoplast from fungi or yeasts (Hamlyn et al., 1981). A number of commercially available enzyme preparations useful in the enzymatic lysis of yeast and fungal cells are available. Such products normally comprise multiple enzymatic activities, e.g. including .beta.-(1-3)- and/or .beta.-(1-6)-glucanase, protease, chitinase, mannanase and other enzymes capable of cleaving cell wall components.
Dubourdieu et al., (1985) (Carbohydrate Research, 144, 277-287), have investigated an industrial enzyme preparation (Novo Industri A/S) derived from a strain of Trichoderma harzianum which, among other glucanases, comprises a .beta.-(1-6)-endoglucanase.
According to Pitson et al., (1993), filamentous fungi such as Penicillium brefeldianum, Trichoderma harzianum and yeasts such as Saccharomyces cerevisiae are known to produce enzymes exhibiting .beta.-(1-6)-endoglucanase activity.
It would be desirable to be able to improve the cell wall degrading or modifying capability of such enzyme preparations and further to be able to more specifically control the degradation or modification of specific cell wall components.